The numpy .tolist method produces nested lists if the numpy array shape is 2D.
if flat lists are desired, the method below works.
import numpy as np
from itertools import chain
a = [1,2,3,4,5,6,7,8,9]
print type(a), len(a), a
npa = np.asarray(a)
print type(npa), npa.shape, "\n", npa
npa = npa.reshape((3, 3))
print type(npa), npa.shape, "\n", npa
a = list(chain.from_iterable(npa))
print type(a), len(a), a`